Half to william f



(No Model.)

B. A. DARLING. CIRCUIT CLOSER FOR BURGLAB ALARMS.

No. 453,466. Patented June 2, 1891.

Izyi,

W Lt71/6656S, I 71,7/(7' 71/1 57" Edwin uiflarziny' ZQ J UNITED STATESPATENT OFFICE.

ED\VIN A. DARLING, OF HOPEDALE, MASSACHUSETTS, ASSIGNOR OF ONE- HALF TOWILLIAM F. DRAPER, OF SAME PLACE.

CIRCUIT-CLOSER FOR BURGLAR-ALARMS.

SPECIFICATION forming part of Letters Patent No. 453,466, dated June 2,1891.

Application filed January 10, 1888. Serial No. 260,349. No model.)

To all whom it may concern.-

Be it known that I, EDWIN A. DARLING, of Hopedale, county of 'Worcester,Stateof Massachusetts,have invented an Improvement in Circuit-Closersfor Burglar-Alarms, of which the following description, in connectionwith the accompanying drawings, is a specifica-,

tion, like letters on the drawings representing like parts.

The object of my invention is to produce a circuit-closer forburglar-alarms or similar apparatus adapted to be operated by thepressure of the foot when stepped upon and of such construction as notto be observed by the person operating it.

Circuit-closers to be operated by the pressure of the foot have beenpreviously made which were concealed in mats to be placed near the doorsor windows, so as to be operated bya person entering the room; but suchcircuit-closers, so far as known to me, have occupied a considerablespace and have sufficient movement in operating to be readily recognizedby persons familiar with such apparatus and are likely to be avoided byexperienced burglars, who know of the existence of circuit-closers inmats, and are thus careful to avoid stepping on a mat or rug whenentering a house.

The present invention consists of a circuitcloser composed of a'pair ofvery thin strips of elastic metal, watch spring steel being preferred,said strips being mechanically connected together, but electricallyinsulated from one another by thin pads or washers of insulatingmaterial, set at short distances from one another-say an inch orso=along the metal strips, which may be of any desired length, and isinclosed in a tubular covering, which protects it and preventsaccidental displacement of the springs. The entire circuitcloser thusconstructed may be less than from one thirty-second to one fiftieth ofan inch thick, and when placed under an ordinary carpet will produce noridge that would make its presence known, and will produce noappreciable wear on the carpet. The elasticity of the springs issufficient to support the weight of the carpet without permitting thesprings to come in contact, but when pressed upon by a heavy weight, aswhen a person treads on the carpet just above one of thesecircuit-closers, the springs will yield and come in contact with oneanother at some point between the insulating-pads, and will thus closean electric circuit, of which the two springs constitute the terminals,and which may contain any suitable alarm apparatus.

Figure 1 is a side elevation of a circuitcloser for burglar alarmsembodying this invention, and Fig. 2 a plan view thereof.

The said circuit-closer consists of two strips a l) of thin elasticconducting materialsteel, such as commonly used for watch-springs, beingwell adapted for this purpose. The said strips are supported one abovethe other and separated from one another a short distance, sufficient toinsulate them, by pads c of insulating material, which may be smallpieces of paper cemented to the springs or otherwise fastened at properdistances apart, the said pads being preferably spaced at aboutthree-fourths of an inch from one another. The conductors d e of anelectric circuit may be soldered to said strips, respectively, whichwill thus form the terminals of the said circuit, and each of saidconductors d 6 may have branches connected, respectively, with thesprings a, and b, and any desired number of the said circuit-closers maybe placed beneath the carpet at any desired part of the room, preferablynear the doors and windows, so that a person cannot enter or leave theroom without stepping on some one of said circuit-closers and thuspressing the upper spring a into contact with the lower spring I) atsome point between the insulatingpads c, and thus closing the circuit.The circuit'closing springs are inclosed in tubular coverings, which maybe a fabric Woven or braided thereon, as shown at f, Fig. 2, or may be athin rubber tube drawn over the springsto prevent them from accidentaldisplacement, and to prevent dust from entering between them so as toimpair the electrical contact when they are pressed together.

The entire circuit-closer as made in actual practice is not over fromone thirty-second to one fiftieth of an inch thick, and when placedunder an ordinary carpet gives no indication of its position, so that aperson aware that such circuit-closers are used would not be able toavoid stepping upon and operating them,

tic strips of conducting material and a number of thin pads ofinsulating material interposed between said conducting-strips at shortdistances from one another along the said conductors, and a tubularcovering inclosing the said springs, substantially as described.

In testimony whereof I have signed my name to this specification in thepresence of two subscribing Witnesses.

EDWIN A. DARLING.

\Vitnesses:

F. J. DU'rcHER, v ARTHUR H. BALL.

